Image projection apparatus

ABSTRACT

An image projection apparatus for projecting an image on a projection plane includes a light source; a light source housing to encase the light source; a ventilation unit to send air to the light source; and a flow path set between the light source housing and a side face of the image projection apparatus. A part of the air sent to the light source, by using the ventilation unit, is flowed into the flow path.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority pursuant to 35 U.S.C. §119 to Japanese Patent Application No. 2012-062108, filed on Mar. 19, 2012 in the Japan Patent Office, the disclosure of which is incorporated by reference herein in its entirety.

BACKGROUND

1. Technical Field

The present invention relates to an image projection apparatus.

2. Background Art

Image projection apparatuses such as projectors can receive image data from personal computers or video cameras to generate an image by using an image generator. The image generator projects and displays the image onto a screen using light emitted from a light source.

The light source of the image projection apparatus may be a halogen lamp, a metal-halide lamp, or a high-pressure mercury vapor lamp, all of which generate heat when they emit light. Therefore, a ventilation unit such as a blower or a fan is used to cool the light source as disclosed in JP-2003-5292-A and WO-02/097529-A.

However, the maximum temperature of the light source become, for example, 1000 Celcius degrees, by which the temperature of a light source housing that encases the light source in a body of the image projection apparatus also becomes high temperature. Such heated light source housing causes the high temperature of a side face of the image projection apparatus such as an outer cover facing the light source housing. If a user touches such hot outer cover, the user may feel such hot outer cover uncomfortable. Therefore, in addition to the ventilation unit to send air to the light source, another ventilation unit to send air to a space between the outer cover and the light source housing may be disposed. However, such another ventilation unit will increase the number of parts, and increasing cost and size of the apparatus.

SUMMARY

As one aspect of the present invention, an image projection apparatus for projecting an image on a projection plane is devised. The image projection apparatus includes a light source; a light source housing to encase the light source; a ventilation unit to send air to the light source; and a flow path set between the light source housing and a side face of the image projection apparatus. A part of the air sent to the light source, by using the ventilation unit, is flowed into the flow path.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendant advantages and features thereof can be readily obtained and understood from the following detailed description with reference to the accompanying drawings, wherein:

FIG. 1 shows a perspective view of a projector according to an example embodiment and a projection plane;

FIG. 2 shows a pattern of light paths from a projector to a projection plane;

FIG. 3 shows a schematic perspective view of a projector;

FIG. 4 shows a perspective view of a main unit of a projector;

FIG. 5 shows a perspective view of an image generation unit;

FIG. 6 shows a schematic perspective view of a light source unit;

FIG. 7 shows a perspective view of an image generation unit and a lighting unit;

FIG. 8 shows a perspective view of the image generation unit of FIG. 7;

FIG. 9 shows a perspective view of a first optical unit with the lighting unit and the image generation unit;

FIG. 10 shows a cross-sectional view along a line D-D of FIG. 9;

FIG. 11 shows a perspective view of a second optical unit configured with a projection lens unit, the lighting unit, and the image generation unit;

FIG. 12 shows a perspective view of the second optical unit configured with the first optical unit, the lighting unit, and the image generation unit;

FIG. 13 shows a schematic view of the light path from the first optical system to a projection plane;

FIG. 14 schematically shows a layout of units in the projector;

FIG. 15 shows an example of use environment of the projector according to an example embodiment;

FIG. 16 shows an example of use environment of a conventional projector;

FIG. 17 shows another example of use environment of a conventional projector;

FIG. 18 shows an example of another use environment of the projector according to an example embodiment;

FIG. 19 shows a perspective view of the projector viewed from a bottom face of the projector;

FIG. 20 shows a perspective view of the projector when an openably closable cover is removed from the projector;

FIG. 21 shows a schematic view of airflow patterns in the projector;

FIG. 22 shows an internal configuration of the projector of FIG. 21;

FIG. 23 shows a cross-sectional view of the projector cut at a line E-E of FIG. 22;

FIG. 24 shows a perspective view of the projector by removing an outer cover; and

FIG. 25 shows a cross-sectional view of a light source housing and its surroundings of the projector.

The accompanying drawings are intended to depict exemplary embodiments of the present invention and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted, and identical or similar reference numerals designate identical or similar components throughout the several views.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

A description is now given of exemplary embodiments of the present invention. It should be noted that although such terms as first, second, etc. may be used herein to describe various elements, components, regions, layers and/or sections, it should be understood that such elements, components, regions, layers and/or sections are not limited thereby because such terms are relative, that is, used only to distinguish one element, component, region, layer or section from another region, layer or section. Thus, for example, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.

In addition, it should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. Thus, for example, as used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Moreover, the terms “includes” and/or “including”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Furthermore, although in describing views shown in the drawings, specific terminology is employed for the sake of clarity, the present disclosure is not limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have the same function, operate in a similar manner and achieve a similar result. Referring now to the drawings, an apparatus or system according to an example embodiment is described hereinafter.

FIG. 1 shows a perspective view of a projector 1 and a projection plane 101. The projector 1 includes, for example, a transparent glass 51, an operation unit 83, and a focus lever 33. As shown in FIG. 1, the projector 1 has the transparent glass 51 on its top face, from which a projection image P is projected to the projection plane 101. The projection image P projected from the transparent glass 51 is displayed on the projection plane 101 such as a screen. Further, the projector 1 has the operation unit 83 on its top face, by which a user can operate the projector 1. Further, the projector 1 has the focus lever 33 on its side face for adjusting the focus of image. Hereinafter, the normal line direction of the projection plane 101 is set as X direction, the short side direction of the projection plane 101 (or top/bottom direction) is set as Y direction, and the long side direction of the projection plane 101 (or horizontal direction) is set as Z direction.

FIG. 2 shows a pattern of light paths from the projector 1 to the projection plane 101. The projector 1 includes, for example, a light source unit having a light source, and an image generator A to generate images using the light emitted from the light source. The image generator A includes, for example, an image generation unit 10, and a lighting unit 20. The projector 1 further includes a projection optical system B.

The image generation unit 10 includes an image generation element such as a digital mirror device (DMD) 12. The lighting unit 20 reflects and irradiates light coming from the light source to the DMD 12 to generate a light image. The projection optical system B projects the light image on the projection plane 101. The projection optical system B includes a least one pass-through type reflection optical system. For example, the projection optical system B includes a first optical unit 30 and a second optical unit 40.

The first optical unit 30 includes, for example, a first optical system 70 of co-axial system having the positive power. The second optical unit 40 includes, for example, a reflection mirror 41, and a curved mirror 42 having the positive power.

The DMD 12 can generate an image using the light emitted from the light source. Specifically, the light emitted from the light source irradiates the DMD 12 and an image is generated by modulating the light irradiated by the lighting unit 20. The image generated by the DMD 12 is projected onto the projection plane 101 via the first optical system 70 of the first optical unit 30, and the reflection mirror 41 and the curved mirror 42 of the second optical unit 40.

FIG. 3 shows a schematic perspective view of an internal configuration of the projector 1. As shown in FIG. 3, the image generation unit 10, the lighting unit 20, the first optical unit 30, the second optical unit 40 are arranged along the Y direction in FIG. 3. Further, a light source unit 60 can be disposed at a right side of the lighting unit 20 in FIG. 3.

Further, as shown in FIG. 3, the first optical unit 30 has a lens holder 32 having legs 32 a 1 and 32 a 2, and the image generation unit 10 has a screw stopper 262 used to fix the image generation unit 10 to the lighting unit 20 using a screw.

A description is given of configuration of each unit. Initially, the light source unit 60 is described. FIG. 4 shows a schematic perspective view of the light source unit 60. The light source unit 60 includes a light-source bracket 62, and a light source 61 fixed on the light-source bracket 62. The light source 61 is, for example, a halogen lamp, a metal-halide lamp, and a high-pressure mercury vapor lamp. Further, the light-source bracket 62 has a connector 62 a connectable to a power-source connector of a power source unit 80 (FIG. 14).

Further, a holder 64 is fixed on the light exiting side of the light source 61 disposed on the light-source bracket 62 by using screws, wherein the holder 64 retains a reflector or the like. Further, a light exiting window 63 is disposed for the holder 64 while the light exiting window 63 is disposed at a side opposite the position of the light source 61. The light emitted from the light source 61 can be guided to the light exiting window 63 by the reflector retained in the holder 64, and exits from the light exiting window 63.

Further, light source position-setting members 64 a 1 to 64 a 3 are disposed at the top face of the holder 64 and both ends of the X direction of the bottom face of the holder 64 so that the light source unit 60 can be positioned correctly on a lighting unit bracket 26 of the lighting unit 20 (FIG. 6). For example, the light source position-setting member 64 a 3 disposed at the top face of the holder 64 has a protruded-shape, and the light source position-setting members 64 a 1 and 64 a 2 disposed at the bottom face of the holder 64 have a hole shape.

Further, a light-source air intake port 64 b is disposed at a side face of the holder 64 to take in air used for cooling the light source 61, and a light-source air exhaust port 64 c is disposed at the top face of the holder 64 to exhaust air heated by the heat of the light source 61.

Further, a pass-through area 65 is disposed for the light-source bracket 62 to take in air sucked in by an air-intake blower 91 (FIG. 20) to be described later. Further, an opening 65 a is disposed at an air-intake side of the pass-through area 65 as shown in FIG. 4 to send a part of airflow flowing into the pass-through area 65 to a space between the light source unit 60 and an openably closable cover 54 (FIG. 19), to be described later. The cooling of the light source unit 60 will be described later.

Further, as shown in FIG. 4, the light source position-setting member 64 a 3 having a protruded-shape is provided on a plane face portion 64 d 2 disposed at the top face of the holder 64, and the light source position-setting members 64 a 1 and 64 a 2 having the hole shape is disposed at a plane face portion 64 d 1 of the bottom face of the holder 64. Such plane face portion 64 d 2 and the plane face portion 64 d 1 can be used as abutting members to be abutted to the lighting unit bracket 26 when pressed by a pressing member of the openably closable cover 54 to be described later.

A description is given of the lighting unit 20 with reference to FIG. 5, which shows a perspective view of optical parts encased in the lighting unit 20 and other units. As shown in FIG. 5, the lighting unit 20 includes, for example, a color wheel 21, a light tunnel 22, two relay lenses 23, a cylinder mirror 24, and a concave mirror 25, wherein such parts can be retained by the lighting unit bracket 26. The lighting unit bracket 26 includes, for example, a casing 261 that encases the relay lenses 23, the cylinder mirror 24, and the concave mirror 25. Among four sides of the casing 261, only one side has a side face (i.e., right side of FIG. 5), and other three sides are opening. Further, an OFF plate 27 (FIG. 6) is disposed at one opening-side of the X direction in FIG. 5, and a cover member is disposed at another opening-side of the X direction in FIG. 5. With such a configuration, the relay lenses 23, the cylinder mirror 24, and the concave mirror 25 encased in the casing 261 of the lighting unit bracket 26 can be covered by the lighting unit bracket 26, the OFF plate 27, and the cover member.

Further, a through-hole 26 d is disposed on the bottom face of the casing 261 of the lighting unit bracket 26 so that the DMD 12 can be exposed through the through-hole 26 d.

Further, the lighting unit bracket 26 includes, for example, three legs 29. Such legs 29 can contact a base member 53 (FIGS. 13, 18, 19) of the projector 1 to support the weight of the first optical unit 30 and the second optical unit 40 stacked and fixed on the lighting unit bracket 26. Further, by providing the legs 29, a space for taking in external air to a heat exchanger such as a heat sink 13 (FIG. 6) that cools the DMD 12 of the image generation unit 10, can be arranged, to be described later.

Further, as shown in FIG. 5, the lens holder 32 of the first optical unit 30 includes, for example, legs 32 a 3 and 32 a 4, and the second optical unit 40 includes, for example, a screw stopper 45 a 3.

FIG. 6 shows a perspective view of the image generation unit 10, the lighting unit 20, and a projection lens unit 31 viewed from the direction C shown in FIG. 5. The casing 261 of the lighting unit bracket 26 has a top face 26 b extending in a direction perpendicular to the Y direction of FIG. 6. Through-holes are disposed at four corners of the top face 26 b to fasten the first optical unit 30 with screws by inserting the screws into the through-holes. For example, FIG. 6 shows the through-holes 26 c 1 and 26 c 2.

Further, as shown in FIG. 6, position-setting holes 26 e 1 and 26 e 2 are respectively disposed next to the through-holes 26 c 1 and 26 c 2 to set the first optical unit 30 at a correct position with the lighting unit 20. As for such position-setting holes 26 e 1 and 26 e 2, the position-setting hole 26 e 1 disposed at the color wheel 21 side is used as a primary position-setting hole having a circular hole shape, and the position-setting hole 26 e 2 disposed at an opposite side of the color wheel 21 is used as a secondary position-setting hole having a slot hole extending in the Z direction.

Further, a position-setting protrusion 26 f is disposed around each of the through-holes 26 c 1 and 26 c 2, wherein the position-setting protrusion 26 f protrudes from the top face 26 b of the lighting unit bracket 26. The position-setting protrusion 26 f is used to set the first optical unit 30 at a correct position in the Y direction.

If the precision of positioning is to be enhanced in the Y direction without providing the position-setting protrusion 26 f, the flatness of the entire top face of the lighting unit bracket 26 is required to be enhanced, which is costly. By providing the position-setting protrusion 26 f, the flatness is required to be enhanced only at the position-setting protrusion 26 f. Therefore, the precision of positioning can be enhanced in the Y direction while reducing the cost.

Further, the top face of the lighting unit bracket 26 has an opening covered by a light shield plate 262 engaging the lower end of the projection lens unit 31, by which the intrusion of light from the upper side into the casing 261 can be prevented.

Further, the top face 26 b of the lighting unit bracket 26 has a cutout between the through-holes 26 c 1 and 26 c 2 of the top face 26 b so that the second optical unit 40 can be screwed to the first optical unit 30 easily, to be described later.

A light source positioning member 26 a 3 is disposed at one end of the lighting unit bracket 26 at the color wheel 21 side (Z direction in FIG. 6). The light source positioning member 26 a 3 has a cylinder-like shape having a through-hole, to which the light source position-setting member 64 a 3 having the protruded-shape (FIG. 4), disposed at the top face of the holder 64 of the light source unit 60, engages. Further, two light source positioning members 26 a 1 and 26 a 2 having protruded-shape are disposed at a lower side of the light source positioning member 26 a 3, to which the light source position-setting member 64 a 1 and 64 a 2 disposed on the holder 64 at the light-source bracket 62 side, which are through-holes, engage respectively. By respectively engaging the light source position-setting members 64 a 1 to 64 a 3 disposed for the holder 64 to the light source positioning members 26 a 1 to 26 a 3 disposed for the lighting unit bracket 26 of the lighting unit 20, the light source unit 60 can be fixed at the correct position of the lighting unit 20 (FIG. 3).

Further, the lighting unit bracket 26 includes a lighting unit cover 28 that covers the color wheel 21 and the light tunnel 22.

FIG. 7 shows a light path L of light in the lighting unit 20. The color wheel 21 has a disc shape and is fixed on a motor shaft of a color motor 21 a. The color wheel 21 includes, for example, R (red), G (green), and B (blue) filters along the rotation direction. The light focused by a reflector disposed for the holder 64 of the light source unit 60 passes through the light exiting window 63, and then reaches the peripheral area of the color wheel 21. The light that has reached the peripheral area of the color wheel 21 is separated into R, G, B lights along the timeline as the color wheel 21 rotates.

The lights separated by the color wheel 21 enter the light tunnel 22. The light tunnel 22 is a tube-shaped member having a square-like cross shape, and its internal face is finished as a mirror face. The light entered the light tunnel 22 reflects a plurality of times on the internal face of the light tunnel 22, and is then emitted as uniform light to the relay lenses 23.

The light that has passed the light tunnel 22 passes the two relay lenses 23, reflects on the cylinder mirror 24 and the concave mirror 25, and is then focused on an image generation face of the DMD 12 as an image.

A description is given of the image generation unit 10 with reference to FIG. 8, which shows a perspective view of the image generation unit 10. As shown in FIG. 8, the image generation unit 10 includes, for example, a DMD board 11 to which the DMD 12 is attached. The DMD 12 is attached to a socket 11 a disposed on the DMD board 11 while orienting an image generation face composed of micro minors arranged in a lattice pattern to an upward direction. The DMD board 11 includes a drive circuit to drive micro minors.

A heat exchanger such as the heat sink 13 is fixed on a distal side of the DMD board 11 (i.e., a face opposite a face having the socket 11 a) to cool the DMD 12. The DMD board 11 has a through-hole area to which the DMD 12 is attached, and the heat sink 13 has a protruded portion 13 a (FIG. 7) insertable into the through-hole area. The protruded portion 13 a has an edge portion having a flat shape. By inserting the protruded portion 13 a into the through-hole area, the flat edge portion of the protruded portion 13 a can contact the distal side of the DMD 12 (i.e., face opposite the image generation face). An elastic and flexible heat conduction sheet can be attached on the flat edge portion of the protruded portion 13 a and/or an area of the distal side of the DMD 12 so that the heat sink 13 and the distal side of the DMD 12 can be closely contacted to enhance the thermal conductivity.

The heat sink 13 can be fixed on a face opposite a face disposed of the socket 11 a of the DMD board 11 by applying pressure using a fixing device 14. The fixing device 14 includes, for example, a plate-like fixing part 14 a at a right distal side of the DMD board 11 (right side in FIG. 8), and a plate-like fixing part 14 a at a left distal side of the DMD board 11 (left side in FIG. 8) disposed at as counterpart members with each other. As shown in FIG. 8, one end and other end of the plate-like fixing parts 14 a are linked by a pressure member 14 b extending in the Z direction in FIG. 8.

When the image generation unit 10 is fixed to the lighting unit bracket 26 (FIG. 6) using screws, the heat sink 13 is pressed and fixed to the face opposite the face disposed of the socket 11 a of the DMD board 11 by applying force from the fixing device 14.

A description is given of fixing of the lighting unit bracket 26 of the image generation unit 10. Initially, the image generation unit 10 is positioned with respect to the lighting unit bracket 26 so that the DMD 12 can face the through-hole 26 d disposed on the bottom face of the lighting unit bracket 26 of the lighting unit 20 (FIG. 5). Then, a screw is inserted into each of through-holes disposed for the fixing part 14 a, and each of through-holes 15 disposed for the DMD board 11 from a lower side, and the screw is screwed into each of screw holes disposed at the bottom face of the screw stopper 262 (FIG. 3) of the lighting unit bracket 26 to fix the image generation unit 10 to the lighting unit bracket 26. Further, as the screw is screwed into the screw stopper 262 disposed for the lighting unit bracket 26, the pressure member 14 b presses the heat sink 13 toward the DMD board 11. With such a configuration, the heat sink 13 can be pressed and fixed on the face opposite the face disposed with the socket 11 a of the DMD board 11 by using the fixing device 14.

As such, the image generation unit 10 can be fixed to the lighting unit bracket 26, and the three legs 29 shown in FIG. 5 can support the weight of the image generation unit 10.

The image generation face of the DMD 12 is composed of a plurality of movable micro mirrors arranged in a lattice pattern. Each of micro mirrors can incline the mirror face about a torsion shaft for a given angle, and can be set with two conditions of “ON” and “OFF”. When the micro mirror is set “ON,” the light coming from the light source 61 is reflected toward the first optical system 70 (FIG. 2) as shown by an arrow L2 shown in FIG. 7. When the micro mirror is set “OFF,” the light coming from the light source 61 is reflected toward the OFF plate 27, retained on the side face of the lighting unit bracket 26 shown in FIG. 6, as shown by an arrow L1 shown in FIG. 7. Therefore, by driving each mirror independently, the light projection can be controlled for each pixel of image data to generate an image.

The light reflected to the OFF plate 27 is absorbed as heat and then the OFF plate 27 is cooled by the airflow flowing outside of the OFF plate 27.

A description is given of the first optical unit 30 with reference to FIG. 9, which shows a perspective view of the first optical unit 30 with the lighting unit 20 and the image generation unit 10. As shown in FIG. 9, the first optical unit 30 is disposed over the lighting unit 20, and includes, for example, the projection lens unit 31, and the lens holder 32. The projection lens unit 31 retains the first optical system 70 (FIG. 2) composed of a plurality of lenses, and the lens holder 32 retains the projection lens unit 31. The lens holder 32 is disposed with four legs 32 a 1 to 32 a 4 extending toward the downside, wherein FIG. 9 shows the legs 32 a 2 and 32 a 3. The leg 32 a 1 is shown in FIG. 3, and the leg 32 a 4 is shown in FIG. 5. Each of the legs 32 a 1 to 32 a 4 is formed of a screw hole on its bottom face to be used when fixed with the lighting unit bracket 26 using a screw.

Further, the projection lens unit 31 is disposed with a focus gear 36 meshed with an idler gear 35. The idler gear 35 is meshed with a lever gear 34, and the focus lever 33 is fixed to a rotation shaft of the lever gear 34. As shown in FIG. 1, the end of the focus lever 33 is exposed outside of the projector 1.

When the focus lever 33 is operated, the focus gear 36 is rotated via the lever gear 34 and the idler gear 35. When the focus gear 36 is rotated, each of the plurality of lenses composing the first optical system 70 disposed in the projection lens unit 31 can be moved to a given direction to adjust a focus point of a projection image.

Further, the lens holder 32 includes, for example, four threaded through-holes 32 c 1 to 32 c 3 so that the second optical unit 40 can be fixed with the first optical unit 30 using screws, in which a screw 48 is screwed into each of the threaded through-holes 32 c 1 to 32 c 3. FIG. 9 shows three threaded through-holes 32 c 1 to 32 c 3, and the screw 48 is inserted into each of the threaded through-holes 32 c 1 to 32 c 3. In FIG. 9, the end of the screw 48 is shown. Further, positioning protruded members 32 d 1 to 32 d 3 are respectively formed around each of the threaded through-holes 32 c 1 to 32 c 3, in which each of the positioning protruded members 32 d 1 to 32 d 3 protrudes from the face of the lens holder 32. FIG. 9 shows the positioning protruded members 32 d 1 to 32 d 3.

FIG. 10 shows a cross-sectional view along a line D-D of FIG. 9. As shown in FIG. 10, each of the legs 32 a 1 and 32 a 2 is disposed with positioning protruded members 32 b 1 and 32 b 2, respectively. The positioning protruded member 32 b 1 (right side in FIG. 10) is inserted in the position-setting hole 26 e 1 having the circular hole shape, which is the primary position-setting hole disposed on the top face 26 b of the lighting unit bracket 26. The positioning protruded member 32 b 2 (left side in FIG. 10) is inserted in the position-setting hole 26 e 2 having the slot hole shape, which is the secondary position-setting hole. With such a configuration, the position in the Z direction and X direction can be set correctly.

Further, a screw 37 is inserted into each of the through-holes 26 c 1 to 26 c 4 disposed for the top face 26 b of the lighting unit bracket 26, and then screwed into screw holes of each of the legs 32 a 1 to 32 a 4 of the lens holder 32, by which the first optical unit 30 can be fixed to the lighting unit 20 with a correct position.

The second optical unit 40 includes a mirror holder 45 (FIG. 12) that covers a portion of the projection lens unit 31 above the lens holder 32 to be described later. Further, as shown in FIG. 3, a space between a part of the lens holder 32, lower than a part of the lens holder 32 corresponding to the projection lens unit 31 and the top face 26 b of the lighting unit bracket 26 of the lighting unit 20 is exposed outside. However, because the projection lens unit 31 engages the lens holder 32, the light does not enter the light path of projection light from such exposed part.

A description is given of the second optical unit 40 with reference to FIG. 11 and FIG. 12. FIG. 11 shows a perspective view of the second optical unit 40 used as a second optical system configured with the projection lens unit 31, the lighting unit 20, and the image generation unit 10. As shown in FIG. 11, the second optical unit 40 includes, for example, the reflection mirror 41, and the curved mirror 42 having the concave shape. The reflection face of the curved mirror 42 can be finished as a circular face, a rotation symmetrical non-circular face, a free curve shape, or the like.

FIG. 12 shows a perspective view of the second optical unit 40 with the first optical unit 30, the lighting unit 20, and the image generation unit 10. The second optical unit 40 passes the light reflected from the curved mirror 42, and includes the transparent glass 51 to prevent intrusion of dust to optical parts in the projector 1.

The second optical unit 40 includes, for example, a mirror bracket 43, a free mirror bracket 44, and a mirror holder 45. The mirror bracket 43 retains the reflection mirror 41 and the transparent glass 51. The free mirror bracket 44 retains the curved mirror 42. The mirror holder 45 holds the mirror bracket 43 and the free mirror bracket 44.

The mirror holder 45 has a box-like shape while the upper side, lower side, and one side such as right side in the X direction in FIG. 12 are opened, and thereby the mirror holder 45 has a U-like shape when viewed from the top. The upper part of the mirror holder 45 includes an inclined portion extending along a direction set between the middle of the X and Y directions by increasing the height, and includes a parallel face parallel to the X direction. The inclined portion is disposed at a proximal side of the parallel face in the X direction. Further, the peripheral side of upper opening of the mirror holder 45 disposed at a proximal side in the X direction and extending in the Z direction is parallel to the Z direction in FIG. 12.

The mirror bracket 43 is attached to the upper part of the mirror holder 45. The mirror bracket 43 includes an inclined side 43 a and a horizontal side 43 b. The inclined side 43 a rises along a direction set between the middle of the X and Y directions by increasing the height as shown in FIG. 12. The horizontal side 43 b extends in a direction parallel to the X direction in FIG. 12. The inclined side 43 a contacts the peripherals of the inclined portion of the mirror holder 45, and the horizontal side 43 b contacts the peripherals of the horizontal part of the mirror holder 45, which is the top of the mirror holder 45. The inclined side 43 a includes an opening, and the reflection mirror 41 is retained to cover the opening of the inclined side 43 a. The horizontal side 43 b includes an opening, and the transparent glass 51 is retained to cover the opening of the horizontal side 43 b.

Each end of the reflection mirror 41 in the Z direction is pressed to the inclined side 43 a of the mirror bracket 43 by the mirror pressing member 46 such as a leaf spring to hold the reflection mirror 41 at the inclined side 43 a of the mirror bracket 43. For example, as shown in FIG. 12, one end of the reflection mirror 41 in the Z direction is fixed by the two mirror pressing members 46, and other end of the reflection mirror 41 in the Z direction is fixed by the one mirror pressing member 46.

Each end of the transparent glass 51 in the Z direction is pressed to the horizontal side 43 b of the mirror bracket 43 by a glass pressing member 47 such as a leaf spring to hold the transparent glass 51 on the mirror bracket 43. Each end of the transparent glass 51 in the Z direction is retained by using one glass pressing member 47 at each end in the Z direction.

The free mirror bracket 44 to retain the curved mirror 42 includes an arm portion 44 a at each side of the free mirror bracket 44, in which the arm portion 44 a extends and inclines along a direction set between the middle of the X and Y directions as shown in FIG. 12. Further, the free mirror bracket 44 includes a link portion 44 b that links such two arm portions 44 a at the upper portion of the arm portions 44 a. The arm portion 44 a of the free mirror bracket 44 is attached to the mirror holder 45 so that the curved mirror 42 covers an opening of the minor holder 45.

The curved mirror 42 pressed toward the link portion 44 b of the free mirror bracket 44 by a free mirror pressing member 49 such as a leaf spring at a substantially center of one end side of the transparent glass 51. Further, each end side of the first optical system 70 in the Z direction in FIG. 12 is fixed to the arm portion 44 a of the free mirror bracket 44 using a screw.

The second optical unit 40 is stacked and fixed on the lens holder 32 of the first optical unit 30. Specifically, the bottom side of the minor holder 45 has a bottom face 451 that faces an upper face of the lens holder 32. The bottom face 451 has three screw stoppers 45 a 1 to 45 a 3 having tube-like shape, which can be fixed with the first optical unit 30 by screws. FIG. 12 shows the screw stoppers 45 a 1 and 45 a 2, and FIG. 5 shows the screw stopper 45 a 3. The second optical unit 40 is fixed to the first optical unit 30 using screws, in which the screw 48 is inserted into each of the threaded through-holes 32 c 1 to 32 c 3 provided for the lens holder 32 of the first optical unit 30, and screwed into each of the screw stoppers 45 a 1 to 45 a 3 to fix the second optical unit 40 to the first optical unit 30.

In such a configuration, the bottom face of the mirror holder 45 of the second optical unit 40 contacts the positioning protruded members 32 d 1 to 32 d 3 of the lens holder 32, by which the second optical unit 40 can be fixed at a correct position in Y direction.

As shown in FIG. 12, when the second optical unit 40 is stacked and fixed on the lens holder 32 of the first optical unit 30, a portion of the projection lens unit 31 that is above the lens holder 32 is encased in the mirror holder 45 of the second optical unit 40. Further, when the second optical unit 40 is stacked and fixed on the lens holder 32, a space is set between the curved mirror 42 and the lens holder 32, and the idler gear 35 (FIG. 9) may be set in such space.

FIG. 13 shows a schematic view of the light path from the first optical system 70 to the projection plane 101 such as a screen. The light flux that has passed through the projection lens unit 31 configuring the first optical system 70 is used to generate an intermediate image between the reflection mirror 41 and the curved mirror 42, which is a conjugate image with respect to an image generated by the DMD 12. Such intermediate image is generated as a curved image between the reflection mirror 41 and the curved mirror 42. Such intermediate image enters the curved mirror 42 having a concave shape, and the curved mirror 42 enlarges the intermediate image and projects the enlarged image onto the projection plane 101.

As such, an optical projection system can be configured with the first optical system 70, and the second optical system. In such a configuration, the intermediate image is generated between the first optical system 70 and the curved mirror 42 of the second optical system, and the intermediate image is enlarged and projected by the curved mirror 42, by which the projection distance to the screen can be set shorter. Therefore, the projector 1 can be used in small meeting rooms or the like.

Further, as shown in FIG. 13, the first optical unit 30 and the second optical unit 40 are stacked and fixed to the lighting unit bracket 26. Further, the image generation unit 10 is fixed to the lighting unit bracket 26. Therefore, the legs 29 of the lighting unit bracket 26 can be fixed to the base member 53 while supporting the weight of the first optical unit 30, the second optical unit 40, and the image generation unit 10.

FIG. 14 schematically shows a layout of units in the projector 1. As shown in FIG. 14, the image generation unit 10, the lighting unit 20, the first optical unit 30, and the second optical unit 40 are stacked along the Y direction, which is the short side direction of the projection plane 101. As shown in FIG. 14, the light source unit 60 is arranged in the Z direction with respect to other stacked units composed of the image generation unit 10, the lighting unit 20, the first optical unit 30, and the second optical unit 40, which is the long side direction of the projection plane 101. As such, in an example embodiment, the image generation unit 10, the lighting unit 20, the first optical unit 30, the second optical unit 40, and the light source unit 60 can be arranged along the Y direction and Z directions, which are parallel to a projection image and the projection plane 101.

Specifically, a projection optical system B having the first optical unit 30 and the second optical unit 40 is stacked on the image generator A having the image generation unit 10 and the lighting unit 20. The light source unit 60 is coupled to the image generator A in a direction perpendicular to the stacking direction of the image generator A and the projection optical system B. Further, the image generator A and the light source unit 60 can be arranged along a direction parallel to the base member 53. Further, the image generator A and the projection optical system B may be arranged along a direction perpendicular to the base member 53, in which the image generator A is disposed over the base member 53, and then the projection optical system B is disposed over the image generator A.

Further, as shown in FIG. 14, a power source unit 80 is stacked or disposed above the light source unit 60, wherein the power source unit 80 supplies power to the light source 61 and the DMD board 11. The light source unit 60, the power source unit 80, the image generator A, and the projection optical system B are encased in a casing of the projector 1. The casing of the projector 1 includes the top face of the projector 1, the base member 53, and an outer cover 59 (FIG. 18) used as the side face of the projector 1 to be described later.

FIG. 15 shows an example of use environment of the projector 1 according to an example embodiment, and FIGS. 16 and 17 show examples of use environment of conventional projectors 1A and 1B. As shown in FIGS. 15 to FIG. 17, when the projector is used in a meeting room, the projector may be placed on a table 100, and images are projected on the projection plane 101 such as a white board.

As shown in FIG. 16, as for the conventional projector 1A, the DMD 12, the lighting unit 20, the first optical system 70, and the second optical system such as the curved mirror 42 are serially arranged along in the direction perpendicular to the projection plane 101 to which a projection image is projected. Therefore, the length of the projector 1A in the direction perpendicular to the projection plane 101 (i.e., X direction) becomes longer, and thereby a greater space is required for the projector 1A in the direction perpendicular to the projection plane 101.

Typically, chairs that participants sit and desks that participants use may be arranged in the direction perpendicular to the projection plane 101 when to see images projected on the projection plane 101. Therefore, if a greater space for the projector 1A is required in the direction perpendicular to the projection plane 101, the arrangement space for chairs and the arrangement space for desks are restricted and thereby not convenient when the projector is used.

As shown in FIG. 17, as for the conventional projector 1B, the DMD 12, the lighting unit 20, and the first optical system 70 are serially arranged along in a direction parallel to the projection plane 101 to which a projection image is projected. Therefore, compared to the projector 1A shown in FIG. 16, the length of the projector 1B in the direction perpendicular to the projection plane 101 can be set shorter. However, as for the projector 1B of FIG. 17, the light source 61 is arranged in the direction perpendicular to the projection plane 101 and is arranged after the lighting unit 20 in the direction perpendicular to the projection plane 101, and thereby the length of the projector 1B in the direction perpendicular to the projection plane 101 may not be effectively set shorter.

As for the projector 1 of an example embodiment shown in FIG. 15, the image generator A having the image generation unit 10 and the lighting unit 20, and the projection optical system B having the first optical unit 30 and the reflection mirror 41 are serially arranged along in a direction parallel to the projection plane 101, to which a projection image is projected. In such a configuration, the image generator A and the projection optical system B are serially arranged along in a direction parallel to the Y direction in FIG. 15. Further, the light source unit 60 and the lighting unit 20 are serially arranged along in a direction parallel to the projection plane 101, which means the light source unit 60 and the lighting unit 20 are serially arranged along the Z direction in FIG. 15.

As such, as for the projector 1 according to an example embodiment, the light source unit 60, the image generation unit 10, the lighting unit 20, the first optical unit 30, and the reflection mirror 41 can be arranged in a direction parallel to the projection plane 101 such as the Z direction or Y direction in FIG. 15. As such, the light source unit 60, the image generation unit 10, the lighting unit 20, the first optical unit 30, and the reflection mirror 41 can be arranged in a direction parallel to the projection plane 101 such as the Z direction or Y direction in FIG. 15. Therefore, the length of the projector 1 in the direction perpendicular to the projection plane 101 (i.e., X direction in FIG. 15) can be set shorter than the length of the projectors 1A and 1B shown in FIG. 16 and FIG. 17.

With such a configuration, the projector 1 may not cause problems when arranging a space for chairs and desks, by which the projector 1 having a good enough level of convenience can be devised.

Further, as shown in FIG. 14, the power source unit 80 is stacked or disposed above the light source unit 60 to supply power to the light source 61 and the DMD board 11, by which the length of the projector 1 in the Z direction can be set shorter.

FIG. 18 shows another example use of the projector 1 according to an example embodiment. As shown in FIG. 18, the projector 1 can be fixed on a ceiling 105. Because the projector 1 has a short side in the direction perpendicular to the projection plane 101, the projector 1 can be fixed on the ceiling 105 without interfering a lighting device 106 disposed on the ceiling 105.

Further, although the second optical system may be configured with the reflection mirror 41 and the curved mirror 42, but the second optical system can be configured with only the curved mirror 42. Further, the reflection mirror 41 can be a plane mirror, a mirror having a positive refractive power, and a mirror having a negative refractive power. Further, the curved mirror 42 may be a concave mirror or a convex mirror. When the curved mirror 42 is a convex mirror, the first optical system 70 is configured in a way so that no intermediate image is generated between the first optical system 70 and the curved mirror 42.

Because the light source 61 has a lifetime for effective use, the light source 61 is required to be replaced with a new one periodically. Therefore, the light source unit 60 is detachably attached to a body of the projector 1.

FIG. 19 shows a perspective view of the projector 1 viewed from a bottom face of the projector 1, wherein the bottom face may be placed on a table. As shown in FIG. 19, the bottom face of the projector 1 includes the base member 53 and the openably closable cover 54. The openably closable cover 54 includes a rotate-able member 54 a. When the rotate-able member 54 a is rotated, the openably closable cover 54 is unlocked from the body of the projector 1, by which the openably closable cover 54 can be removed from the body of the projector 1. Further, the base member 53 includes, for example, a power-source air intake port 56 at a position next to the openably closable cover 54 in the X direction.

Further, as shown in FIG. 19, an air-intake port 84 and the input unit 88 are disposed on one Y-X plane of the outer cover 59 of the projector 1. The input unit 88 is used to input image data from external apparatuses such as personal computers.

FIG. 20 shows a perspective view of the projector 1 when the openably closable cover 54 is removed from the projector 1. When the openably closable cover 54 is removed, the light-source bracket 62 of the light source unit 60 is exposed, wherein the exposed side is the opposite side that the light source 61 is attached. The light-source bracket 62 includes a knob 66, which is pivotable about the pivot center 01 indicated by a dotted line in FIG. 20.

When removing the light source unit 60 from the body of the projector 1, the knob 66 is pivoted and opened by picking the knob 66, by which the light source unit 60 can be removed from an opening of the body of the projector 1. When attaching the light source unit 60 into the body of the projector 1, the light source unit 60 is inserted into the body of the projector 1 through the opening. When the light source unit 60 is inserted into the body of the projector 1, the connector 62 a (FIG. 4) is connected with a power-source connector in the body of the projector 1, and the three light source position-setting members 64 a 1 to 64 a 3 of the holder 64 (FIG. 4) engage with three light source positioning members 26 a 1 to 26 a 3 (FIG. 6) disposed for the lighting unit bracket 26 of the lighting unit 20, by which the light source unit 60 is set at a correct position in the body of the projector 1, and the attachment of the light source unit 60 completes. Then, the openably closable cover 54 is attached to the base member 53.

As such, the knob 66 is provided for the light source unit 60, but the pass-through area 65 shown in FIG. 20, which protrudes to the openably closable cover 54 can be used as a knob. The pass-through area 65 may be also referred to as the duct 65.

Further, the base member 53 is disposed with three legs 55. By rotating the legs 55, the protruded length of the legs 5 from the base member 53 can be changed, by which the height adjustment in the Y direction of the projector I can be conducted.

Further, as shown in FIG. 20, an exhaust port 85 is disposed at other Y-X plane of the outer cover 59.

FIG. 21 shows a schematic view of airflow in the projector 1 according to an example embodiment. FIG. 21 shows the projector 1 viewed from the X direction, wherein the X direction is perpendicular to the projection plane 101. FIG. 22 shows a cross-sectional view of an internal configuration of the projector 1 corresponding to the view of FIG. 21. The arrows shown in FIG. 21 and FIG. 22 indicate directions of airflow. FIG. 23 shows a cross-sectional view of the projector 1 cut at line E-E in FIG. 22.

As shown in FIG. 21, the projector 1 includes the air-intake port 84 disposed its one face (left side in FIG. 21), and the exhaust port 85 disposed its other face (right side in FIG. 21). The air-intake port 84 has an opening to intake external air into the projector 1. The exhaust port 85 has an opening to exhaust air from the projector 1. Further, an exhaust fan 86 is disposed at a position facing the exhaust port 85.

When the projector 1 is viewed from the X direction, which is a direction perpendicular to the projection plane 101, a part of the exhaust port 85 and a part of the air-intake port 84 may be disposed between the light source unit 60 and the operation unit 83. Further, a flow path is set between a rear face of the curved mirror 42 and the outer cover 59 facing the rear face of the curved mirror 42 so that air can flow in such space.

With such a configuration, the external air taken from the air-intake port 84 can flow through along the Z-Y plane of the mirror holder 45 of the second optical unit 40 (FIG. 12), and the rear face of the curved mirror 42 by following the mirror holder 45 and curving of the rear face of the curved mirror 42, and then flow to the exhaust port 85.

Further, the curved mirror 42 is a concave-shaped mirror having the positive refractive power as above mentioned, and thereby the rear face of the curved mirror 42 has a convex shape.

Further, the power source unit 80 has a configuration having three sides. Therefore, when the power source unit 80 disposed over the light source unit 60 is viewed from the Z direction in FIG. 21, the power source unit 80 can be viewed as a U-shape configuration without a side facing the light source unit 60. Further, the external air taken from the air-intake port 84 flows along the mirror holder 45 and the curving of the rear face of the curved mirror 42 toward the exhaust port 85, and then further flows to a space encircled by the power source unit 80 having the three sides, and is then exhausted from the exhaust port 85.

As such, the part of the exhaust port 85 and the air-intake port 84 are disposed between the light source unit 60 and the operation unit 83 when the projector 1 is viewed from the X direction, which is a direction perpendicular to the projection plane 101. In such a configuration, an airflow passing through a space between the light source unit 60 and the operation unit 83 and exhausted from the exhaust port 85 can be generated.

Further, a light source blower 95 is disposed at a position that can suck air around the color motor 21 a (FIG. 5) that drives the color wheel 21 in the lighting unit 20. With such a configuration, the color motor 21 a and the light tunnel 22 can be cooled using the airflow generated by the air sucking effect of the light source blower 95.

The air sucked in by the light source blower 95 passes a light source duct 96, and then flows into a light-source air supply port 64 b (FIG. 4) of the holder 64. Further, a part of the air flowing into the light source duct 96 flows into a space between a light source housing 97 and the outer cover 59 from an opening 96 a formed on a face of the light source duct 96 opposing the outer cover 59 (FIG. 19).

The air flowing into the space between the light source housing 97 and the outer cover 59 from the opening 96 a of the light source duct 96 cools the light source housing 97 and the outer cover 59, and is then exhausted from the exhaust port 85 using the exhaust fan 86, which will be described later.

Further, the air flowing to the light-source air supply port 64 b flows into the light source 61 to cool the light source 61, and is then exhausted from the light-source air exhaust port 64 c disposed on the top face of the holder 64. The air exhausted from the light-source air exhaust port 64 c is then exhausted from an opening formed on the top face of the light source housing 97 toward the exhaust port 85 along a fluid guide 87 as shown in FIG. 22. Then, the air exhausted from the light source housing 97 (i.e., high-temperature air) is mixed with external air (i.e., low-temperature air) that flows around the second optical unit 40 and then flows into the space encircled by the power source unit 80, and then the mixed air is exhausted from the exhaust port 85 using the exhaust fan 86. As such, the high-temperature air exhausted from the light-source air exhaust port 64 c is mixed with the external air (i.e., low-temperature air), and then exhausted from the exhaust port 85. Therefore, the temperature of air exhausted from the exhaust port 85 can be decreased to a lower temperature.

Further, the fluid guide 87 can be omitted from the configuration. For example, even without the fluid guide 87, the high temperature air exhausted from the light-source air exhaust port 64 c can be exhausted from the exhaust port 85 because the high temperature air can be mixed with low-temperature air flowing from the air-intake port 84 toward the exhaust port 85, which flows along the rear face of the curved mirror 42, at a space surrounded by a power factor correction (PFC) main power source board 80 a and a PFC sub-power source board 80 a, to be described later.

However, by disposing the fluid guide 87, a direct hit of high temperature air exhausted from the light-source air exhaust port 64 c to the PFC main power source board 80 a and the PFC sub-power source board 80 a can be prevented.

However, if the fluid guide 87 blocks the entire flow of high temperature air exhausted from the light-source air exhaust port 64 c toward the PFC main power source board 80 and the PFC sub-power source board 80 a, the high temperature air may not be mixed with the low-temperature air flowing along the rear face of the curved mirror 42, by which the high temperature air is exhausted from the exhaust port 85 without decreasing its high temperature air, thereby the exhaust port 85 becomes high temperature.

Therefore, it is preferable that the air exhausted from the light-source air exhaust port 64 c and passing the fluid guide 87 passes the space surrounded by the PFC main power source board 80 a and the PFC sub-power source board 80 a, by which the air exhausted from the light-source air exhaust port 64 c can be mixed with the low-temperature air flowing from the air-intake port 84 toward the exhaust port 85, and then the air is exhausted from the exhaust port 85 by decreasing its high temperature, which is safer for a user.

Further, the operation unit 83 is preferably disposed on a top face of the projector 1 so that the user can operate the operation unit 83 easily. Because the projector 1 includes the transparent glass 51 on its top face for projecting images on the projection plane 101, the operation unit 83 may be disposed on a position corresponding to the light source 61 when viewing the projector 1 from the Y direction.

As such, the low-temperature air, flowing through a space between the light source unit 60 and the operation unit 83 from the air-intake port 84 toward the exhaust port 85, can be used to cool the high-temperature air, which has become high temperature when the air has cooled the light source 61, by which the low-temperature air and high-temperature air become mixed air. Such mixed air is then exhausted from the exhaust port 85, and thereby the movement of high temperature air to the operation unit 83 can be prevented.

With such a configuration, the temperature increase of the operation unit 83, which may be caused by the high temperature air coming from the light source 61, can be prevented. Further, a part of air, flowing from the air-intake port 84 to the exhaust port 85, flows around the second optical unit 40 and then under the operation unit 83 to cool the operation unit 83. Therefore, the temperature increase of the operation unit 83 can be prevented.

Further, when the exhaust fan 86 sucks in air, external air can be sucked from the power-source air intake port 56 disposed on the base member 53 (FIG. 19). A ballast board to supply power or current to the light source 61 is disposed at a position distal of the light source housing 97 in the X direction of FIG. 21. The external air sucked from the power-source air intake port 56 can flow through a space between the light source housing 97 and the ballast board in the upward direction to cool the ballast board. Then, the air flows to a space encircled by the power source unit 80 disposed over the ballast board, and is then exhausted from the exhaust port 85 using the exhaust fan 86.

In an example embodiment, a fan to generate the airflow from the air-intake port 84 to the exhaust port 85 is disposed at an exhaust side, in which the exhaust fan 86 is used as such fan. If the fan is provided at the exhaust side, the air supply volume from the air-intake port 84 into the projector 1 can be set greater than a fan disposed near the air-intake port 84.

If the fan is disposed near the air-intake port 84, the flow rate of external air supplied into the projector 1 may be decreased because the second optical unit 40 exists in a direction that the fan supplies air.

In contrast, if the fan (e.g., exhaust fan 86) is disposed near the exhaust port 85, the flow rate exhausted from the exhaust fan 86 may not decrease because objects may not exist outside the exhaust port 85. Therefore, when a given volume of air is exhausted from the exhaust fan 86, the same volume of air can be taken from the air-intake port 84, by which the air volume supplied from the air-intake port 84 into the projector 1 may not decrease. Therefore, the air can flow from the air-intake port 84 toward the exhaust port 85 at a given wind pressure, by which hot air rising from the light source 61 can effectively flow to the exhaust port 85 using the air flow flowing from the air-intake port 84 toward the exhaust port 85.

Further, a cooling unit 120 to cool the heat sink 13 of the image generation unit 10 and the light-source bracket 62 of the light source unit 60 is disposed at the lower left side of the projector 1 as shown in FIG. 21. The cooling unit 120 includes, for example, an air-intake blower 91, a vertical duct 92 disposed under the air-intake blower 91, and a horizontal duct 93 connected at the bottom of the vertical duct 92.

The air-intake blower 91 is disposed at a lower side of the air-intake port 84 while facing the air-intake port 84. The air-intake blower 91 sucks external air from the air-intake port 84 via a side face of the air-intake blower 91 facing the air-intake port 84, and also sucks air from the body of the projector 1 from another side, opposite the side face of the air-intake blower 91 facing the air-intake port 84. Such sucked airflows in the vertical duct 92 disposed under the air-intake blower 91. The air flowing into the vertical duct 92 flows downward, and then flows to the horizontal duct 93 connected at the bottom of the vertical duct 92.

As shown in FIG. 21, the heat sink 13 is present in the horizontal duct 93. Therefore, the heat sink 13 can be cooled by the air flowing in the horizontal duct 93. By cooling the heat sink 13, the DMD 12 can be cooled effectively and efficiently, by which high temperature of the DMD 12 can be prevented.

The air flowing through the horizontal duct 93 flows into the pass-through area 65 (duct 65) or the opening 65 a disposed for the light-source bracket 62 of the light source unit 60 (FIG. 4). The air flowing into the opening 65 a flows through a space between the openably closable cover 54 and the light-source bracket 62, and cools the openably closable cover 54.

Meanwhile, the air flowing into the pass-through area 65 cools the light-source bracket 62, and then flows into a space opposite the light exit side of the light source 61 to cool a face of a reflector 67 (FIG. 25) so that the reflector 67 of the light source 61 is cooled, in which the face of the reflector 67 cooled by the air is a face opposite the reflection face of the reflector 67. Therefore, the air that passes through the pass-through area 65 can take heat from both of the light-source bracket 62 and the light source 61.

The air, which has passed near the reflector 67, passes through an exhaust duct 94, which is used to guide the air from the top side of the light-source bracket 62 to the lower side of the exhaust fan 86, and then converges into the air exhausted from the light-source air exhaust port 64 c, and then flows to the exhaust port 85, and then the air can be exhausted from the exhaust port 85 using the exhaust fan 86.

Further, the air flowing into a space between the openably closable cover 54 and the light-source bracket 62 through the opening 65 a cools the openably closable cover 54, and then flows inside the projector 1, and is then exhausted from the exhaust port 85 using the exhaust fan 86.

The heat generated at the light source 61 heats the light source housing 97 used as a housing of the light source 61, by which the light source housing 97 becomes hot. Then, such hot light source housing 97 heats the outer cover 59, which is a side face of the projector 1 facing the light source housing 97, by which the temperature of the outer cover 59 increases. Specifically, the hot light source housing 97 heats the outer cover 59 from an inner side face of the outer cover 59. If the temperature of the outer cover 59 increases, the outer cover 59 becomes high temperature and hot. If a user touches such hot outer cover 59 of the projector 1, the user may feel uncomfortable. To prevent such uncomfortable condition, it is preferable to set the temperature of the outer cover 59 at a given level such as 95 Celcius degrees or less, or more preferably 75 Celcius degrees or less.

In view of such temperature condition, the light source duct 96 is formed with the opening 96 a as above described so that a part of air sucked by the light source blower 95 can be flowed into a space between the light source housing 97 and the outer cover 59 through the opening 96 a. A description is given of the opening 96 a of the light source duct 96.

FIG. 24 shows a perspective view of the projector 1 when the outer cover 59 is removed. In FIG. 24, the light source blower 95 is disposed in front of the light source housing 97 in the X direction. The light source blower 95 is used to suck air in the projector 1 from both side faces of light source blower 95. The exhaust port of the light source blower 95 is connected to an air intake end of the light source duct 96. The light source duct 96 extends through an opening formed on the light source housing 97, and an exhaust end of the light source duct 96 faces the light-source air supply port 64 b formed on a face of the holder 64 of the light source unit 60 encased in the light source housing 97.

FIG. 25 shows a cross-sectional view of the light source housing 97 of the projector 1. As shown in FIG. 25, the light source duct 96 is inclined from the light source blower 95 to the light source 61. The air sucked by the light source blower 95 moves in the light source duct 96 from left to right in FIG. 25, and then takes a flow path extending toward the light source 61, and flows to the light-source air supply port 64 b.

The opening 96 a of the light source duct 96 is formed on a wall face of the light source duct 96, which is one side the flow path of the light source duct 96. A part of the air flowing from the light source blower 95 straightforwardly hits a wall face of the light source duct 96. Therefore, by providing the opening 96 a on the wall face of the light source duct 96, a part of the air flowing in the light source duct 96 can be smoothly flowed to a space between the light source housing 97 and the outer cover 59 through the opening 96 a. The size and shape of the opening 96 a can be changed in view of the flow rate through the opening 96 a. For example, the flow rate through the opening 96 a can be set at one fifth of the flow rate into the light source 61.

The air flowing through the opening 96 a flows in the space between the light source housing 97 and the outer cover 59 in a direction from left to right in FIG. 25. After cooling the outer cover 59 and the light source housing 97, the air moves upward by the suction power of the exhaust fan 86, and is then exhausted from the exhaust port 85 by using the exhaust fan 86.

Meanwhile, the air flowing from the light source duct 96 to the light source 61 via the light-source air supply port 64 b cools the light source 61 as above described, and then passes through the light-source air exhaust port 64 c and the opening formed on the top face of the light source housing 97, and then moves the upward direction from the light source housing 97. Further, such air is mixed with low-temperature air, taken from the upper part of the air-intake port 84 using the exhaust fan 86, and then the mixed air is exhausted from the exhaust port 85 by using the exhaust fan 86.

As such, the light source housing 97 can be cooled by the air flowing through the space between the outer cover 59 and the light source housing 97. With such a configuration, the temperature increase of the outer cover 59, which may be caused by heat of the light source housing 97, can be suppressed, and the outer cover 59 can be cooled. Therefore, the temperature increase of the outer cover 59 can be effectively suppressed. With such a configuration, even if a user touches such outer cover 59, facing the light source housing 97, the user may not feel uncomfortable. In contrast, if the temperature of the outer cover 59 is too high, the user may feel uncomfortable.

Further, by cooling the light source housing 97, the temperature increase of the light source 61 can be suppressed, and the light source 61 can be cooled effectively.

The above-described image projection apparatus such as the projector 1 that projects an image on a projection plane may have following effects. The projector 1 includes the light source 61, and a ventilation unit such as the light source blower 95 to send air to the light source 61. The projector 1 includes the flow path, which is a space between the light source housing 97 and the side face of the projector 1 (e.g., outer cover 59). A part of air, being supplied to the light source 61 by using the ventilation unit, can pass the flow path. In the projector 1, the light source housing 97 encases the light source 61 in the projector 1. With such a configuration, the light source housing 97 can be cooled, and the temperature increase of the outer cover 59 caused by the heat of the light source housing 97 can be suppressed. Because the outer cover 59 can be also cooled, the temperature increase of the outer cover 59 can be effectively suppressed. With such a configuration, the outer cover 59 facing the light source housing 97 can be prevented from becoming too hot or high temperature condition.

Further, the projector 1 includes a duct such as the light source duct 96 to flow air to the light source 61 from the ventilation unit such as the light source blower 95. The light source duct 96 is formed with the opening 96 a on its wall face to flow air to the space between the light source housing 97 and the side face of the projector 1 (e.g., outer cover 59). With such a configuration, a part of air flowing into the light source duct 96 from the ventilation unit such as the light source blower 95 can flow to the space between the light source housing 97 and the outer cover 59.

In the above described example embodiment, an image projection apparatus such as the projector 1 can suppress the temperature increase of the side face of the image projection apparatus while suppressing the cost and size increase of the apparatus.

In the above described example embodiment, air to be send to the light source by using the ventilation unit is partially flowed to a space between the light source housing and the side face of the image projection apparatus to cool the side face of the image projection apparatus and the light source housing. With such a configuration, the temperature increase of side face of the image projection apparatus can be suppressed. Further, such partial airflow to the space between the light source housing and the inner side face of the image projection apparatus can be supplied using one ventilation unit that supplies air to the light source. Therefore, the cost and size of the image projection apparatus can be suppressed compared to a configuration employing one ventilation unit to send air to the light source and another ventilation unit to send air to the space between the light source housing and the side face of the image projection apparatus.

Numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the disclosure of the present invention may be practiced otherwise than as specifically described herein. For example, elements and/or features of different examples and illustrative embodiments may be combined each other and/or substituted for each other within the scope of this disclosure and appended claims. 

What is claimed is:
 1. An image projection apparatus for projecting an image on a projection plane, comprising: a light source; a light source housing to encase the light source; a ventilation unit to send air to the light source; and a flow path set between the light source housing and a side face of the image projection apparatus, a part of the air sent to the light source, by using the ventilation unit, is flowed into the flow path.
 2. The image projection apparatus of claim 1, further comprising a duct connecting the ventilation unit and the light source for flowing air from the ventilation unit to the light source, wherein the duct has a wall face formed with an opening, through which the part of the air is flowed to the flow path set between the light source housing and the side face of the image projection apparatus. 